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Showing 3 results for Khavandi
MECHANICAL PROPERTIES OF DENTAL COMPOSITE MATERIALS REINFORCED WITH MICRO AND NANO-SIZE Al2O3 FILLER PARTICLES
F. Foroutan, J. Javadpou, A. Khavandi, M. Atai, H. R. Rezaie,
Volume 8, Issue 2 (spring 2011 2011)
Abstract
Abstract: Composite specimens were prepared by dispersion of various amounts of nano-sized Al2O3 fillers in a monomer system containing 60% Bis-GMA and 40% TEGDMA. For comparative purposes, composite samples containing micrometer size Al2O3 fillers were also prepared following the same procedure. The mechanical properties of the light- cured samples were assessed by three-point flexural strength, diametral tensile strength, and microhardness tests. The results indicated a more than hundred percent increase in the flexural strength and nearly an eighty percent increase in the diametral tensile strength values in the samples containing nano-size Al2O3 filler particles. It is interesting to note that, this improvement was observed at a much lower nano-size filler content. Fracture surfaces analyzed by scanning electron microscopy, indicated a brittle type of fracture in both sets of specimens.
In Vitro Release Kinetics of Curcumin From Thermosensitive Gelatin-Chitosan Hydrogels Containing Zinc Oxide Nanoparticles
Shadi Moshayedi, Hossein Sarpoolaky, Alireza Khavandi,
Volume 19, Issue 2 (June-Biomaterials Special Issue- 2022)
Abstract
In this paper, chemically-crosslinked gelatin/chitosan hydrogels containg zinc oxide nanoparticles (ZNPs), were loaded with curcumin (CUR), and their microstructural features, physical properties, curcumin entrapment efficiency, and drug release kinetics were evaluated using scanning electron microscopy (SEM), the liquid displacement method, and UV–Vis spectroscopy. The in vitro kinetics of drug release was also studied using First-order, Korsmeyer-Peppas, Hixon-Crowell, and Higuchi kinetic models. The SEM micrographs confirmed the formation of highly porous structures possessing well-defined, interconnected pore geometries. A significant reduction in the average pore sizes of the drug-loaded hydrogels was observed with the addition of ZNPs and CUR to the bare hydrogels. High value of drug loading efficiency (~ 72 %) and maximum drug release of about 50 % were obtained for the drug-loaded scaffolds. It was found that curcumin was transported via the non-Fickian diffusion mechanism. It was also shown that the kinetics of curcumin release was best described in order by Hixon-Crowell, Higuchi, and Korsmeyer-Peppas models, demonstrating that drug release was controlled by diffusion, degradation, and swelling of the drug carrier. However, lower degree of fitting was observed with First-order kinetic model.

Resin-based Copper-free Brake Pads: A Right Selection of Potassium Titanate and Ceramic Fiber
Hamid Ansari, Saeed Banaeifar, Reza Tavangar, Alireza Khavandi, Soheil Mahdavi,
Volume 19, Issue 3 (September 2022)
Abstract
The present study aimed to assess the effect of replacing copper as a multi-functional ingredient in the brake pad material with potassium titanate platelet (PTP) and a particular type of ceramic fiber (CF) copper-free composite. Chase dynamometer tests were conducted to compare a brake padchr('39')s tribological behavior when PTP and CF are added to the composition with that of the copper-bearing pad. The results concluded that PTP and CF demonstrated promising outcomes such as a stable coefficient of friction (COF), lower wear rate, and better heat resistance in copper-free friction composite. Scanning electron microscope (SEM/EDS) analysis was conducted to investigate the role of main elements such as Ti, Fe, K, O, and C on the formation of contact plateaus (CPs) upon the worn surface of friction composites. PTP maintained both continuous contact and smooth friction braking application of a brake pad. The uniform distribution of Ti on the wear track on the disc worn surface depicts the role of PTPs on stabilizing the friction film formation and eventually on the stability of COF.
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